Hobart correspondent for Fairfax Media

The sea came for Port Arthur in a midwinter high tide, with a south-south-easterly storm pushing waves up the cove and an intense low above.

The waves tore down a jetty and threw seawall boulders aside. The foundations of Australia's best known convict-era building, the penitentiary, were flooded with saltwater.

The immediate clean-up and repair cost $180,000. The inundation worsened the task of preserving the already fragile jail.

It could cost $6 million to restore and make safe, Port Arthur's chairman, Barry Jones, said last week. Part of this restoration work may be an engineered line of defence against the sea, said the site's building conservation manager, Jo Lincoln.

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In the site's 182-year history there had been perhaps one – less intense – sea flood, about 40 years ago, she said. But the July 2011 storm was a harbinger. Lincoln said they were "fully convinced" it would happen again.

This week as we reflect on the tepid response to climate change at Doha, it seems there needs to be more wake-up calls like the Port Arthur flood.

Graphs and charts aren't enough. The cold calculations of scientists and dire warnings of climate sages are not translating into strong action. We need to see dramatic evidence of damage.

That's why the disintegration of Antarctica's Larsen B ice shelf in February 2002 was so timely. And why Great Barrier Reef bleaching events grab our attention.

It's also why the Witness King Tides project this week is a chance to gather more resonant images.

The CSIRO says the consequences of sea level rise for Australia will include increased flooding of coastal land, erosion, loss of beaches and higher storm surges.

About 85 per cent of the Australian population live within 50 kilometres of the coast and will see inundation and more frequent storms hitting their built environment.

This Friday morning king tides will come to Sydney and Hobart. As the Witness King Tides map shows you can track their timing around the country and contribute your image of the effect.

Depending on the weather's intensity, some of these king tides may be like Port Arthur's inundation.

As always, on the one hand we face the task of teasing out the natural variability of these inundations from climate change. And on the other hand we risk the change we document being rapidly less reversible.

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